A fuel cell system includes a fuel cell that generates electricity through an electrochemical reaction between a fuel gas and an oxidizing gas (reaction gases), a gas supplying flow path that supplies the reaction gases to the fuel cell, and a gas discharging flow path that discharges the reaction gases from the fuel cell. Open/close valves for the fuel cell can be provided in the gas supplying flow path and the gas discharging flow path.
For example, an open/close valve for a fuel cell discussed in Japanese Unexamined Patent Application Publication No. 2004-183713 includes a valve member having a columnar portion, which is movable in its axial direction to close or open the gas flow path. This open/close valve for a fuel cell includes a diaphragm that divides an inside space into two chambers and is provided at a hydrogen discharging portion where hydrogen exhausted from the fuel cell is discharged. A path branched from an air supplying path, which supplies air to the fuel cell, is connected to one chamber of the two chambers of the open/close valve. A coil spring is provided in the other chamber of the two chambers. The coil spring urges the valve member to open the other chamber and discharge the discharged hydrogen. If air is supplied to one chamber of the valve in an operating state, a pressure acts on the diaphragm to cause the valve member to contact a valve seat against an elastic force of the coil spring while the other chamber is closed.
A pressure regulating valve for a fuel cell discussed in Japanese Unexamined Patent Application Publication No. 2006-49103 is provided upstream in a hydrogen flow path that supplies anode side hydrogen to a fuel cell stack. The pressure regulating valve for a fuel cell includes a diaphragm, which divides an inside space into a pressure regulating chamber and a back-pressure chamber. An upstream side branch flow path, which is branched from an upstream side hydrogen flow path, supplies hydrogen into the back-pressure chamber of the pressure regulating valve.
According to the above-described open/close valve for a fuel cell discussed in Japanese Unexamined Patent Application Publication No. 2004-183713, improvement in view of operability of valve is possible. More specifically, there is a problem (Problem 1) that water may freeze at an inner side edge opening peripheral portion of a valve of an air supply tube connected to an open/close valve. Moreover, there is another problem (Problem 2) that the air supply tube may be broken or deformed in a travelling condition of a fuel cell vehicle that installs a fuel cell system including the open/close valve.
For example, regarding the above-described Problem 1, in the case of the open/close valve for a fuel cell discussed in Japanese Unexamined Patent Application Publication No. 2004-183713, if water vapor is present in the air supplied to one chamber of the two chambers partitioned by the diaphragm, water adheres to an open/close valve inner end portion of the air supply tube if liquefied from the water vapor and may freeze at a low temperature below the freezing point. If the water freezes into ice at an edge portion of the tube that supplies air freezes in this manner, the ice may close the edge portion of the tube and prevent the air from being smoothly supplied or discharged to or from that chamber.
In particular, the air in the one chamber causes large pressure changes between a high pressure and a low pressure according to operations of the valve and therefore causes radical changes in temperature. A large amount of water vapor can be present in the one chamber because it has a relatively large volume compared to the air supply tube. Therefore, the water liquefied from the water vapor tends to adhere to the side edge portion of one chamber. The operational performance of the valve may deteriorate if the adhered water freezes. In this respect, the open/close valve for a fuel cell discussed in Japanese Unexamined Patent Application Publication No. 2004-183713 includes structure capable of preventing water from freezing in the vicinity of the side edge portion of the air supply tube. For example, the air supply tube does not have any edge portion structure capable of preventing the freezing of water.
In the pressure regulating valve discussed in Japanese Unexamined Patent Application Publication No. 2006-49103, hydrogen from the hydrogen tank side is supplied to the back-pressure chamber of the pressure regulating valve. Therefore, no air is introduced into the back-pressure chamber. It is unnecessary, or almost unnecessary, to consider the adhesion of water at a back-pressure chamber side edge portion of the tube connected to the back-pressure chamber. Therefore, the pressure regulating valve discussed in Japanese Unexamined Patent Application Publication No. 2006-49103 has no tube structure capable of preventing the freezing of water at the edge portion of the tube connected to the valve.
In the open/close valve or the pressure regulating valve discussed in Japanese Unexamined Patent Application Publication No. 2004-183713 or Japanese Unexamined Patent Application Publication No. 2006-49103, a connecting portion of the tube (e.g., the air supply tube) is not set to the lowest point on a wall portion of the one chamber or the back-pressure chamber of the two chambers separated by the diaphragm. Therefore, if only one tube is considered, water may not adhere to the edge portion of the tube, compared to the case where the connecting portion of the tube is set to the lowest point of the one chamber or the back-pressure chamber. However, the open/close valve or the pressure regulating valve discussed in Japanese Unexamined Patent Application Publication No. 2004-183713 or Japanese Unexamined Patent Application Publication No. 2006-49103 do not include two pressure chambers, except for the flow path forming pressure chamber constituting a flow path. Therefore, there is no force to caused by a pressure difference between two pressure chambers which can act on a drive shaft of the valve member. For example, other than the chamber and back-pressure chamber partitioned by the diaphragm, the pressure chamber is the only flow path forming pressure chamber constituting a flow path in the open/close valve or the pressure regulating valve discussed in Japanese Unexamined Patent Application Publication No. 2004-183713 or Japanese Unexamined Patent Application Publication No. 2006-49103. As described above, according to the open/close valve or the pressure regulating valve discussed in Japanese Unexamined Patent Application Publication No. 2004-183713 or Japanese Unexamined Patent Application Publication No. 2006-49103, pressure variations caused in the flow path forming pressure chamber due to valve opening/closing operations influence the displacement of the drive shaft. Therefore, improvement of the operability of these valves is possible.
Regarding the above-described Problem 2, in a fuel cell vehicle equipped with a fuel cell system including the fuel cell open/close valve discussed in Japanese Unexamined Patent Application Publication No. 2004-183713 or the pressure regulating valve discussed in Japanese Unexamined Patent Application Publication No. 2006-49103, there is no effective structure capable of preventing the tube connected to the open/close valve from colliding with a foreign object (e.g., snow or a bouncing stone) coming from the front end of the vehicle in motion, and preventing the tube from being deformed (broken or bent). If the tube deforms due to collision with a foreign object, the operational performance of the valve may deteriorate in the same manner as when ice adheres to the tube.
An object of the present invention is to improve, in a valve for a fuel cell and in a fuel cell vehicle, the operational performance of the valve.